In vitro cellular immune functions are being studied in a masked method in patients with ocular toxoplamosis, pars planitis, Behcet's disease, ocular sarcoid, birdshot retinochoroidopathy, geographic choroiditis, and chorioretinitis of unknown origin. Crude ocular antigens, as well as the purified uveitogenic soluble antigen (S-antigen) of the retina, are being used in a lymphocyte microculture technique to evaluate the presence of cellular immune memory to ocular tissues. A subgroup of patients with posterior uveitis has been identified as having this immunologic memory. Other studies concentrate on the presence of suppressor cell activity, functioning of macrophages, and lymphocyte subsets as defined in these patients by monoclonal antibodies. These results shed light on the basic mechanisms of uveitis and may be used as a guide for specific immunologic therapy.